Structural and thermal properties of La2O3Fe2O3P2O5 glasses

The structural properties of xLa2O3(40 − x)Fe2O360P2O5(x = 0, 2, 4, 6, 8, 10 mol%) glasses have been investigated by Fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The FTIR spectra show that the replacement of up to 6 mol% Fe2O3 by La2O3 does not produce any fundamental change in the glass structure, which consists predominantly of pyrophosphate, Q1 units. XRD analysis has confirmed that the majority of samples are X-ray amorphous, and crystallization occurs when the sample containing 8 mol% La2O3, the crystalline phase is LaPO4. The XRD analysis indicates that the solubility of lanthanum oxide in these iron phosphate melts is less than 8 mol%. Glass transition temperature (Tg) and (Tr − Tg) increase as the lanthanum content of the glass is increased. This result suggests that the glass network is strengthening and the thermal stability is improved with the addition of La2O3.